Wednesday, April 26, 2017

Rolling Dams (Drowning Machines), Revisited

I first learned of the danger posed by the typical dam design found in many Midwest rivers when I researched the Yorkville, IL dam. Here are two videos that better describe that danger.

A four minute video that demonstrates the danger.

A 24 minutes video that explains the "hydraulic jump" that causes the rolling current that causes the drownings. It is the backwards rolling current generated near the face of the dam that causes these dams to be called "rolling dams." Another thing I learned is that all of the air trapped in the recirculating current makes it foamy and even harder to swim in.

When I first saw the above video many moons ago, I also found a video that trains first responders how to do a safe rescue. Unfortunately, I now can't find that video. If I remember correctly, the jest of the video was to first string a rope from one bank to the other.

(new window) Even a relatively big outboard motor is of no use.   I'm glad someone cropped this profile video into the following horizontal format.

An unflippable whitwater raft has been developed that allows rescue workers to approach the face of a dam.
Screenshot @ -0:21

(new window)   I learned of this video because he asked for permission to use one of my videos. Since it is licensed CC BY, he didn't need permssion. But I was glad to learn about the video. I see at 4:55 that this is the video that used it.

Cornelia Reade-Hale shared:
Removal of Kentucky dam where multiple people have drowned set to begin Tuesday [June 8,2021]
"Multiple people have drowned at the dam, most recently in October 2018 when 35-year-old kayaker Matthew Hughes, of Lexington, got sucked into the undertow after holding onto a rope for nearly two minutes."

This video scares me just to watch it. That water was up to his knees and flowing pretty fast. And there is a foamy hydraulic jump of at least a foot or so at the base of the dam.

The Kankakee, IL and Wilmington, IL Dams each have Class C hydraulic jump (submerged and rolling).

Carpentersville, IL Dam seems to be designed to create a Class A (stretched out and safe) hydraulic jump. But I still would not want to try going over that dam!

Hofmann Dam in Riverside, IL, is an example where an obsolete mill dam has been removed.

The Montgomery, IL Dam also appears to have a safer design.

This video should get you started on other videos of dam removals.

Of the 13 dams that used to be on the Fox River in Illinois, two of them have already been removed. There are plans to remove the Carpentersville, IL Dam, even though it has one of the safer designs.

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